“The fact that we operate this far north and in mountainous areas, means that we can expect to see snow on the ground somewhere in the country at any time of the year. We have to be prepared for winter conditions all year,” says Captain Svenn Oddli, Scandinavian Airlines’ Chief Pilot on the MD80/MD90. “But it is not until September/October that we can regularly expect winter conditions.”
Captain Håkon Grosvold, Chief Pilot on the Boeing 737 with Braathens, agrees. “In September a crew may start in Kristiansand on the south coast in warm late-summer weather. Flying north to Tromsø or Longyearbyen, they may land in full winter conditions. Such variations are very much the case all winter. Conditions vary extremely from region to region.”
In order to meet this challenge the two companies have special winter operations procedures. Each autumn SAS publishes a Winterization Bulletin preparing crews for the coming season. “In addition we publish an extra Chief Pilot Office Information with special focus on the special aspects of the Norwegian winter. We especially highlight the conditions up north,” explains Capt Oddli. SAS draws pilots from the three participating nations in the airline. The climate in Sweden and Denmark is different from that of Norway, and SAS has chosen to have stringent rules for flying to certain airports in northern Norway. “We require a special check-out to fly to northern Norway. In practice this means that Oslo-based crews are rostered on these routes—plus a few Stockholm-based crews that bid in order to maintain this qualification. Where Kirkenes and Longyearbyen are concerned there are also restrictions on rostering first officers, whereby only Oslo-based first officers are scheduled. Longyearbyen requires a special checkout and only a handful captains are checked out. We do this to ensure frequent visits to this airport half way to the North Pole and with the nearest alternate some 500nm away.” The checkout includes simulator and theory training, and a training flight with either one of the chief pilots, an instructor or a line check pilot.
Braathens also publish a reminder of what is in store for the aircrews when winter comes. “We operate into airports that have relatively short runways with terrain restrictions,” explains Capt Grosvold. “Some of the airports are on islands, others are in the mountains or surrounded by mountains. All these factors influence our operations all year. However, we are especially vary in the wintertime.” Since all of Braathens’ aircrew are based in Norway, there are no special checkouts for winter operations. However, the training follows the same pattern as at SAS with theoretical and practical training. Once on line duty, new first officers are rostered alongside experienced captains.
“Our operations are divided in two,” explains Capt Arne Hegge, Chief Pilot on the Dash-8 with Widerøe’s Flyveselskap. “Roughly half of our services are flown on the STOLport system. The remainder are regional routes. The challenges on the regional routes are the same as the ones Braathens and SAS meet. The STOLports are a different story. Here the longest runways are rarely over 1,000m (3,280 ft) with the majority only 800m (2,625ft) long. Terrain restrictions in the shape of mountains and/or fjords preclude longer runways.”
The three chief pilots agree that once at cruise altitude there are few, if any special problems weatherwise. Even though the main characteristic of the Norwegian weather is variation—a euphemism for instability—there are times when a winter high pressure ‘sits’ on Scandinavia feeding cold weather over the region. During these conditions a peculiar phenomenon occurs: “In extremely cold weather,” says Capt Grosvold, “you can’t trust the altimeter blindly. At minus 30°C the difference in indicated altitude and actual altitude can be up to a thousand feet. The altimeter may be indicating 6,000ft, but you are actually only 5,000ft above sea level. This is particularly critical in a country so mountainous as Norway where tall mountains are frequent on approaches. We have issued a set of tables that give the altitude correction for the applicable temperatures. Our SOP requires that the crew use them in extremely cold weather.”
Another potentially dangerous condition occurs around the freezing point. When moist air hits the colder surface of a wing, it forms a thin layer of ice which distorts the wing profile and reduces lift. Left unchecked it can lead to the aircraft stalling. These conditions are most frequently found at lower altitudes.
“Our STOLport operation is particularly challenging on account of the topography and flying at relatively low altitudes due to short legs,” says Capt Hegge. “Icing can be found from ground level and up to about 16,000ft, but rarely above that. The risk of icing is greatest when the ground temperature is between +3° C (37° F) and -2° C (28° F) with wet precipitation before and during take-off. The altitudes most exposed to icing are between 2,000ft and 14,000ft—depending on the intensity of the precipitation, topography, wind, and temperature at altitude.
